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Abstract:

A nitrogen oxide reduction baffle for a heat exchanger of a furnace and a
gas furnace incorporating at least one such baffle. In one embodiment,
the baffle includes: (1) a body having a predetermined length,
cross-sectional configuration and longitudinal slot, the longitudinal
slot having a predetermined width and position and (2) a locating
structure coupled to the body and configured to place the body in a
predetermined longitudinal location within a heat exchanger and orient
the slot relative to the heat exchanger, the body laterally constrained
within the heat exchanger when the body is located at the predetermined
longitudinal location.

Claims:

1. A nitrogen oxide reduction baffle for a heat exchanger of a furnace,
comprising: a body having a predetermined length, cross-sectional
configuration and longitudinal slot, said longitudinal slot having a
predetermined width and position; and a locating structure coupled to
said body and configured to place said body in a predetermined
longitudinal location within a heat exchanger and orient said slot
relative to said heat exchanger, said body laterally constrained within
said heat exchanger when said body is located at said predetermined
longitudinal location.

2. The baffle as recited in claim 1 wherein said cross-sectional
configuration is adapted for said heat exchanger, said cross-sectional
configuration is configured to constrain said body laterally within said
heat exchanger when said body is located at said predetermined
longitudinal location.

3. The baffle as recited in claim 1 further comprising a further
structure extending from said body at an end thereof distal from said
locating structure.

4. The baffle as recited in claim 3 wherein said further structure is
configured to constrain said body laterally within said heat exchanger
when said body is located at said predetermined longitudinal location.

5. The baffle as recited in claim 3 wherein said further structure is
configured to provide a reactive surface adapted to create a reaction
with respect to a combustion product.

6. The baffle as recited in claim 3 wherein said further structure is
configured to constrain said body laterally within said heat exchanger
when said body is located at said predetermined longitudinal location and
provide a reactive surface adapted to create a reaction with respect to a
combustion product.

7. The baffle as recited in claim 1 wherein said cross-sectional
configuration is selected from the group consisting of: generally square,
generally pentagonal, generally vertically elongated, and generally
circular.

8. The baffle as recited in claim 1 wherein said body has an acute entry
side.

9. The baffle as recited in claim 1 wherein said predetermined length of
said body is between about 2.270 inches and about 3.375 inches.

10. The baffle as recited in claim 1 wherein said body is formed of a
steel mesh.

11. The baffle as recited in claim 1 wherein said body is formed of
perforated steel.

12. The baffle as recited in claim 1 wherein said predetermined width of
said slot is between about 0.200 inches and about 0.220 inches.

13. The baffle as recited in claim 1 wherein said slot extends along an
entirety of a length of an upper surface of said body.

14. A gas furnace, comprising: a housing; a solenoid valve located in
said housing; a manifold coupled to said valve; at least one gas orifice
coupled to said manifold; at least one corresponding heat exchanger
located proximate said at least one gas orifice; a nitrogen oxide
reduction baffle, including: a body having a predetermined length,
cross-sectional configuration and longitudinal slot, said longitudinal
slot having a predetermined width and position, and a locating structure
coupled to said body and configured to place said body in a predetermined
longitudinal location within a heat exchanger and orient said slot
relative to said heat exchanger, said body laterally constrained within
said heat exchanger; and a blower located in said housing proximate said
at least one heat exchanger.

15. The gas furnace as recited in claim 14 wherein said cross-sectional
configuration is adapted for said heat exchanger, said cross-sectional
configuration is configured to constrain said body laterally within said
heat exchanger when said body is located at said predetermined
longitudinal location.

16. The gas furnace as recited in claim 14 further comprising a further
structure extending from said body at an end thereof distal from said
locating structure.

17. The gas furnace as recited in claim 16 wherein said further structure
is configured to constrain said body laterally within said heat exchanger
when said body is located at said predetermined longitudinal location.

18. The gas furnace as recited in claim 16 wherein said further structure
is configured to provide a reactive surface adapted to create a reaction
with respect a combustion product.

19. The gas furnace as recited in claim 14 wherein said cross-sectional
configuration is selected from the group consisting of: generally square,
generally pentagonal, generally vertically elongated, and generally
circular.

20. The gas furnace as recited in claim 14 wherein said body has an acute
entry side.

[0002] This application is directed, in general, to heating, ventilation
and air conditioning (HVAC) systems and, more specifically, to a
self-locating nitrogen oxide (NOx) baffle for a furnace and a gas
furnace incorporating at least one of such baffle.

BACKGROUND

[0003] Combustion heaters of conventional heating systems, also called
furnaces, often employ tubular combustion chambers, also called heat
exchangers, wherein a mixture of gaseous fuel and air is burned, and the
combustion products resulting from the burning are directed to a flue and
ultimately to an exhaust. Air to be conditioned is usually returned from
a living/working space and passed over the tubular combustion chambers,
where it takes on heat from the combustion chambers and then is routed
back to a living or working space. As a result of the combustion process,
combustion systems normally generate gaseous combustion products,
including NOx, which are vented to the atmosphere as flue gas. It is
desirable to limit these NOx emissions since NOx is considered a
pollutant, and combustion systems sold in certain jurisdictions must meet
strict NOx emission standards.

[0004] One technique for limiting NOx emissions from a combustion
system is to control peak combustion flame temperatures that contact the
tubular combustion chambers as well as limiting the residence times at
the peak temperatures to minimize the formation of NOx. It has been
known that peak combustion flame temperatures can be controlled by
locating a flame holder, also called a baffle, into the combustion tube
to contain the flame at least partially and discourage it from directly
contacting the combustion tube. Baffles have been in wide use for many
years in commercial and residential furnaces.

SUMMARY

[0005] One aspect provides a NOx reduction baffle for a heat
exchanger of a furnace. In one embodiment, the baffle includes: (1) a
body having a predetermined length, cross-sectional configuration and
longitudinal slot, the longitudinal slot having a predetermined width and
position and (2) a locating structure coupled to the body and configured
to place the body in a predetermined longitudinal location within a heat
exchanger and orient the slot relative to the heat exchanger, the body
laterally constrained within the heat exchanger when the body is located
at the predetermined longitudinal location.

[0006] Another aspect provides a gas furnace. In one embodiment, the
furnace includes: (1) a housing, (2) a solenoid valve located in the
housing, (3) a manifold coupled to the valve, (4) at least one gas
orifice coupled to the manifold, (5) at least one corresponding heat
exchanger located proximate the at least one gas orifice, (6) a baffle,
having: (6a) a body having a predetermined length, cross-sectional
configuration and longitudinal slot, the longitudinal slot having a
predetermined width and position and (6b) a locating structure coupled to
the body and configured to place the body in a predetermined longitudinal
location within a heat exchanger and orient the slot relative to the heat
exchanger, the body laterally constrained within the heat exchanger and
(7) a blower located in the housing proximate the at least one heat
exchanger.

BRIEF DESCRIPTION

[0007] Reference is now made to the following descriptions taken in
conjunction with the accompanying drawings, in which:

[0008] FIG. 1 is an exploded isometric view of a portion of one embodiment
of a furnace within which a self-locating NOx reduction baffle
constructed according to the principles of the invention may be employed;

[0009]FIG. 2 is an isometric view of inlets of heat exchangers of the
furnace of FIG. 1;

[0010]FIG. 3 is an isometric view of a self-locating NOx reduction
baffle having a generally square cross-sectional configuration and
associated with an inlet of one of the heat exchangers of FIGS. 1 and 2;

[0011] FIGS. 4A-F are various views of the NOx reduction baffle
embodiment of FIG. 3;

[0012] FIGS. 5A-E are various views of a self-locating NOx reduction
baffle having a generally pentagonal cross-sectional configuration that
may be associated with the inlet of a heat exchanger;

[0013] FIGS. 6A-F are various views of a self-locating NOx reduction
baffle having a generally vertically elongated cross-sectional
configuration that may be associated with the inlet of a heat exchanger;
and

[0014] FIGS. 7A-E are various views of a self-locating NOx reduction
baffle having a generally circular cross-sectional configuration that may
be associated with the inlet of a heat exchanger.

DETAILED DESCRIPTION

[0015] Described herein are various embodiments of a self-locating
NOx reduction baffle that may be employed in a furnace. The baffle
is designed to be placed within a heat exchanger, typically proximate an
inlet thereof, where it receives and processes a flame and controls its
dynamics such that concentrations of NOx and perhaps other
combustion products are brought to within desired limits. In various
embodiments, NOx is maintained below 40 nanograms per Joule (ng/J).
In other embodiments, NOx production is maintained substantially below 40
ng/J. In related embodiments, carbon monoxide (CO) is also maintained
below 35 parts per million (ppm). In other embodiments, CO production is
maintained below 9 ppm.

[0016] In general, the baffle moderates the temperature of the flame as it
travels along its length. Moderating the temperature of the flame
includes decreasing maximum temperatures and increasing minimum
temperatures. Decreasing high temperatures reduces NOx production,
and increasing low temperatures reduces CO production. The length and
cross-sectional configuration of the baffle, the width and position of
any longitudinal slot thereof, the material out of which the baffle is
constructed and the location and orientation of the baffle relative to
the heat exchanger potentially affect the manner in which the baffle
processes the flame traveling along its length.

[0017] To address at least some of these objectives and perhaps others,
various baffle embodiments to be introduced herein employ a body having a
predetermined length and cross-sectional configuration and a longitudinal
slot of a predetermined width and position such that the flame is
processed in a desired manner. A locating structure is coupled to the
body and configured to place the body in a predetermined longitudinal
location within a heat exchanger. The locating structure is further
configured to orient the slot relative to the heat exchanger. In some
embodiments, the cross-sectional configuration of the body is also
configured such that when the body is located at its desired position
with the heat exchanger, it is laterally constrained therein. These
embodiments may properly be regarded as "self-locating" baffles. Certain
of the baffle embodiments include a further structure that extends from
the body at an end thereof that is distal from the locating structure. In
some embodiments, the further structure is configured to locate the body
laterally relative to the heat exchanger when it is located at its
desired position therein. These embodiments may also properly be regarded
as self-locating baffles. In other embodiments, the further structure is
configured to provide a reactive surface adapted to create a reaction
with respect to a combustion product (e.g., CO). In a specific
embodiment, the reactive surface is adapted to cause CO to be converted
into CO2, which is generally regarded as being less harmful than CO.

[0018] FIG. 1 is an exploded isometric view of a portion of one embodiment
of a furnace within which a self-locating NOx reduction baffle
constructed according to the principles of the invention may be employed.
The furnace includes a housing 100 having a front opening 105 within
which a mounting shelf 110 is located. The mounting shelf 110 has an
opening 115 therein and supports a heat exchanger assembly 120 over the
opening 115. The illustrated embodiment of the heat exchanger assembly
120 has a row of six heat exchangers (one referenced as 130) coupled to
one another. Alternative embodiments of the heat exchanger assembly 120
have more or fewer heat exchangers coupled to one another in one or more
rows. In the illustrated embodiment, the heat exchangers are generally
serpentine and have three approximately 180° folds such that the
heat exchangers cross over the opening 115 four times, terminating in
inlets 132 and outlets 134 that are generally mutually coplanar and
oriented toward the opening 105 of the housing 100. Alternative
embodiments have alternative heat exchanger configurations.

[0019] A burner assembly 140 contains a thermostatically-controlled
solenoid valve 142, a manifold 144 leading from the valve 142 and across
the burner assembly 150, one or more gas orifices (not shown) coupled to
the manifold 144 and one or more burners (not shown) corresponding to and
located proximate the gas orifices. The illustrated embodiment of the
burner assembly 140 has a row of six burners. Alternative embodiments of
the burner assembly 140 have more or fewer burners arranged in one or
more rows. A flue 146 allows undesired gases (e.g., unburned fuel) to be
vented from the burner assembly 140. In an assembled configuration, the
burner assembly 140 is located proximate the heat exchanger assembly 120
such that the burners thereof at least approximately align with the
inlets 132.

[0020] A draft inducer assembly 150 contains a manifold 152, a draft
inducing exhaust fan 154 having an inlet coupled to the manifold 152 and
a flue 156 coupled to an outlet of the exhaust fan 154. In an assembled
configuration, the draft inducer assembly 150 is located proximate the
heat exchanger assembly 120 such that the manifold 152 thereof at least
approximately align with the outlets 134 and the flue 156 at least
approximately aligns with the flue 146 of the burner assembly 140.

[0021] A blower 160 is suspended from the shelf 110 such that an outlet
(not referenced) thereof approximately aligns with the opening 115. An
electronic controller 170 is located proximate the blower 160 and, in the
illustrated embodiment, controls the blower, the valve 142 and the
exhaust fan 154 to cause the furnace to provide heat. A cover 180 may be
placed over the front opening 105 of the housing 100.

[0022] In the illustrated embodiment, the controller 170 turns on the
exhaust fan to initiate a draft in the heat exchangers (including the
heat exchanger 130) and purge potentially harmful unburned gases or
gaseous combustion products. Then the controller 170 opens the valve 142
to admit gas to the manifold 144 and the one or more gas orifices,
whereupon the gas begins to mix with air to form primary combustion air.
Then the controller 170 activates an igniter (not shown in FIG. 1) to
attempt to ignite the primary combustion air. If the output of a
thermocouple indicates that the primary combustion air has not ignited
within a predetermined period of time, the controller 170 then closes the
valve 142 and waits until attempting to start again. If the output of a
thermocouple indicates that the primary combustion air has ignited within
the predetermined period of time, the controller 170 then activates the
blower, which forces air upward through the opening 115 and the heat
exchanger assembly 120. As it passes over the surfaces of the heat
exchangers, the air is warmed, whereupon it may be delivered or
distributed as needed to provide heating.

[0023]FIG. 2 is an isometric view of inlets of the heat exchangers (one
referenced as 130) of the furnace of FIG. 1. In the embodiment of FIG. 2,
the inlet 132 of the heat exchanger 130 is joined to a faceplate (not
separately referenced) of the burner assembly 120. In one embodiment, a
crimp 234 joins the inlet 234 to the faceplate, forming a ridge that
protrudes slightly forward of the faceplate as shown. A mounting hole 236
is located a predetermined distance and at a predetermined orientation
with respect to the inlet 132. The mounting hole 236 is configured to
allow a NOx reduction baffle (not shown) to be mounted in the heat
exchanger 130. Corresponding mounting holes allow corresponding NOx
reduction baffles (not shown) to be mounted in the other heat exchangers
shown in FIG. 2.

[0024]FIG. 3 is an isometric view of a self-locating NOx reduction
baffle 300 having a generally square cross-sectional configuration and
associated with an inlet of one of the heat exchangers of FIGS. 1 and 2.
In general, the baffle 300 includes a body and a locating structure (both
unreferenced in FIG. 3). The body extends into the inlet 132, and the
locating structure is coupled to the body, extends axially out of the
inlet 132 and then extends radially outward from the inlet 132 where a
fastener 238 (e.g., a screw or bolt) attaches the locating structure to
the faceplate using the hole 236 of FIG. 2. Alternative embodiments
employ other mechanisms, features or structures to attach the baffle 300
to the faceplate.

[0025] FIGS. 4A-F are various views of the NOx reduction baffle
embodiment 300 (the embodiment having a generally square cross-sectional
configuration) of FIG. 3. FIG. 4A is a front-side elevational view; FIG.
4B is a plan view; FIG. 4c is a left-side elevational view; FIG. 4D is an
isometric view; FIG. 4E is a right-side elevational view illustrating the
cross-sectional configuration of the baffle 300; and FIG. 4F is a view of
a flat piece of metal that can be bent to form the baffle 300.

[0026] The baffle 300 includes a body 410 having a predetermined length
and cross-sectional configuration. The baffle 300 also includes a
locating structure. The locating structure includes an insertion portion
420, a crimp-spanning portion 430 and a mounting portion 440. The
insertion portion 420 is coupled to the body 410 and configured to place
the body 410 in a predetermined longitudinal location within a heat
exchanger. The crimp-spanning portion 430 is coupled to the insertion
portion 420 and configured to arch over and span the crimp 234 of FIG. 2.
The mounting portion 440 is coupled to the crimp-spanning portion 430 and
configured to allow the baffle 300 to be attached to another structure
(e.g., the faceplate of FIGS. 2 and 3). When the baffle 300 is attached
to the other structure, the body 410 becomes located at the predetermined
longitudinal location and is laterally constrained within the heat
exchanger.

[0027] The body 410 also has a longitudinal slot 450 having a
predetermined width and position. When the baffle 300 is attached to the
other structure, the slot 450 is also oriented relative to the heat
exchanger. In the illustrated embodiment, assuming the heat exchanger is
properly mounted in the furnace for which it was designed, the slot 450
is oriented such that it is located at or at least near the top of the
body 410. In this orientation, normal convection causes a flame traveling
through the body 410 to rise toward, and perhaps partially exit, the slot
450.

[0028] The mounting portion 440 includes a hole 460 configured to receive
a fastener (e.g., a screw or bolt) that may be employed to attach the
baffle 300. FIG. 4F illustrates that the embodiment of FIGS. 4A-4F may be
constructed of a single piece of metal, perhaps a perforated sheet or
metal mesh. In one embodiment, the metal sheet is grade 310 stainless
steel. In one embodiment, the metal mesh is Kanthal D®, commercially
available from Sandvik AB of Sandviken, Sweden.

[0029] As can be seen particularly in FIGS. 4C and 4E, the body 410 has a
generally square cross-sectional configuration. A flame (not shown)
enters an end of the body 410 proximate the insertion portion 420 and
rises toward the slot 450 as it travels toward and eventually exits a
distal end of the body 410. The length L2 of the insertion portion
420 is sufficient to allow the flame to develop before entering the body
410. In other words, the flame is not partially quenched before entering
the body. This avoids elevated levels of CO production. The flame may at
least partially exit the slot 450 depending upon the width thereof.

[0030] FIGS. 4A-4E set forth various dimensions of the baffle 300. Table
1, below, gives example dimensions for a specific embodiment of the
baffle 300.

Those skilled will recognize, however that other embodiments of the
baffle 300 have dimensions that differ from the values given in Table 1
in whole or in part.

[0031] FIGS. 5A-E are various views of a self-locating NOx reduction
baffle having a generally pentagonal cross-sectional configuration that
may be associated with the inlet of a heat exchanger. FIG. 5A is an
isometric view; FIG. 5B is a plan view; FIG. 5C is a right-side
elevational view; FIG. 5D is a front-side elevational view; and FIG. 5E
is a partial right-side elevational view illustrating the cross-sectional
configuration of the baffle embodiment.

[0032] The baffle 300 includes a body 410 having a predetermined length
and cross-sectional configuration. The baffle 300 also includes a
locating structure. The locating structure includes an insertion portion
420, a crimp-spanning portion 430 and a mounting portion 440. The
insertion portion 420 is coupled to the body 410 and configured to place
the body 410 in a predetermined longitudinal location within a heat
exchanger. The crimp-spanning portion 430 is coupled to the insertion
portion 420 and configured to arch over and span the crimp 234 of FIG. 2.
The mounting portion 440 is coupled to the crimp-spanning portion 430 and
configured to allow the baffle 300 to be attached to another structure
(e.g., the faceplate of FIGS. 2 and 3). When the baffle 300 is attached
to the other structure, the body 410 becomes located at the predetermined
longitudinal location and is laterally constrained within the heat
exchanger.

[0033] The body 410 also has a longitudinal slot 450 having a
predetermined width and position. When the baffle 300 is attached to the
other structure, the slot 450 is also oriented relative to the heat
exchanger. In the illustrated embodiment, assuming the heat exchanger is
properly mounted in the furnace for which it was designed, the slot 450
is oriented such that it is located at or at least near the top of the
body 410. In this orientation, normal convection causes a flame traveling
through the body 410 to rise toward, and perhaps partially exit, the slot
450.

[0034] The mounting portion 440 includes a hole 460 configured to receive
a fastener (e.g., a screw or bolt) that may be employed to attach the
baffle 300. FIG. 4F illustrates that the embodiment of FIGS. 5A-5F may be
constructed of two components: (1) the locating structure that forms the
insertion portion 420, the crimp-spanning portion 430 and the mounting
portion 440 and (2) the body 410 formed of steel mesh and welded or
otherwise fused to the locating structure. In one embodiment, the
locating structure is a grade 310 stainless steel mesh, and the steel
mesh is Kanthal D®.

[0035] As can be seen particularly in FIGS. 5C and 5E, the body 410 has a
generally pentagonal cross-sectional configuration. A flame (not shown)
enters an end of the body 410 proximate the insertion portion 420 and
rises toward the slot 450 as it travels toward and eventually exits a
distal end of the body 410. The length L2 of the insertion portion
420 is sufficient to allow the flame to develop before entering the body
410. In other words, the flame is not partially quenched before entering
the body. This avoids elevated levels of CO production. The flame may at
least partially exit the slot 450 depending upon the width thereof.

[0036] FIGS. 5A-5E set forth various dimensions of the baffle 300. Table
2, below, gives example dimensions for a specific embodiment of the
baffle 300.

Those skilled will recognize, however that other embodiments of the
baffle 300 have dimensions that differ from the values given in Table 2
in whole or in part.

[0037] FIGS. 6A-F are various views of a self-locating NOx reduction
baffle having a generally vertically elongated cross-sectional
configuration that may be associated with the inlet of a heat exchanger.
FIG. 6A is an isometric view; FIG. 6B is a front-side elevational view;
FIG. 6c is a plan view; FIG. 6D is a left-side elevational view; FIG. 6E
is a right-side elevational view; and FIG. 6F is a diagram illustrating
the cross-sectional configuration of the baffle embodiment.

[0038] The baffle 300 includes a body 410 having a predetermined length
and cross-sectional configuration. The baffle 300 also includes a
locating structure. The locating structure includes an insertion portion
420, a crimp-spanning portion 430 and a mounting portion 440. The
insertion portion 420 is coupled to the body 410 and configured to place
the body 410 in a predetermined longitudinal location within a heat
exchanger. The crimp-spanning portion 430 is coupled to the insertion
portion 420 and configured to arch over and span the crimp 234 of FIG. 2.
The mounting portion 440 is coupled to the crimp-spanning portion 430 and
configured to allow the baffle 300 to be attached to another structure
(e.g., the faceplate of FIGS. 2 and 3). When the baffle 300 is attached
to the other structure, the body 410 becomes located at the predetermined
longitudinal location and is laterally constrained within the heat
exchanger.

[0039] The body 410 also has a longitudinal slot 450 having a
predetermined width and position. When the baffle 300 is attached to the
other structure, the slot 450 is also oriented relative to the heat
exchanger. In the illustrated embodiment, assuming the heat exchanger is
properly mounted in the furnace for which it was designed, the slot 450
is oriented such that it is located at or at least near the top of the
body 410. In this orientation, normal convection causes a flame traveling
through the body 410 to rise toward, and perhaps partially exit, the slot
450.

[0040] The mounting portion 440 includes a hole 460 configured to receive
a fastener (e.g., a screw or bolt) that may be employed to attach the
baffle 300. The embodiment of FIGS. 6A-6F may be constructed of a single
piece of metal, perhaps a perforated sheet or metal mesh. In one
embodiment, the metal sheet is grade 310 stainless steel. In one
embodiment, the metal mesh is Kanthal D®, commercially available from
Sandvik AB of Sandviken, Sweden.

[0041] As can be seen particularly in FIGS. 6D and 6E, the body 410 has a
generally vertically elongated cross-sectional configuration. A flame
(not shown) enters an end of the body 410 proximate the insertion portion
420 and rises toward the slot 450 as it travels toward and eventually
exits a distal end of the body 410. Unlike the embodiments of FIGS. 4A-4F
and 5A-5E, the length L7 of the insertion portion 420 is such that
the flame is partially quenched before entering the body 410. The
proximal end of the body 410 also features an acutely angled entry 610.
This has been found further to reduce NOx production, e.g., to below
20 ng/J. However, elevated CO levels result from the partial quenching,
as noted above. To reduce the CO levels, e.g., to acceptable levels, the
embodiment of FIGS. 6A-6F provides a further structure that extends from
the body 410 at an end thereof that is distal from the locating structure
420. The further structure includes a leg portion 620, a bend 630 and a
reactive portion 640. The leg portions 620 is angled with respect to the
body 410 such that the bend 630 contacts the heat exchanger when the
baffle 300 is located at its desired position therein, self-locating the
baffle 300 in the heat exchanger. The reactive portion 640 is exposed to
air flow in the heat exchanger such that its temperature elevates,
configuring it to provide a reactive surface adapted to create a reaction
with respect to a combustion product (e.g., CO). In a specific
embodiment, the reactive surface is adapted to cause CO to be converted
into CO2, which as stated above is generally regarded as being less
harmful than CO. The flame may at least partially exit the slot 450
depending upon the width thereof.

[0042] FIGS. 6A-6F set forth various dimensions of the baffle 300. Table
3, below, gives example dimensions for a specific embodiment of the
baffle 300.

Those skilled will recognize, however that other embodiments of the
baffle 300 have dimensions that differ from the values given in Table 3
in whole or in part.

[0043] FIGS. 7A-E are various views of a self-locating NOx reduction
baffle having a generally circular cross-sectional configuration that may
be associated with the inlet of a heat exchanger. FIG. 7A is an isometric
view; FIG. 7B is a front-side elevational view; FIG. 7c is a plan view;
FIG. 7D is a left-side elevational view; and FIG. 7E is a right-side
elevational view. FIGS. 7E and 7F together illustrate the cross-sectional
configuration of the baffle embodiment.

[0044] The baffle 300 includes a body 410 having a predetermined length
and cross-sectional configuration. The baffle 300 also includes a
locating structure. The locating structure includes an insertion portion
420, a crimp-spanning portion 430 and a mounting portion 440. The
insertion portion 420 is coupled to the body 410 and configured to place
the body 410 in a predetermined longitudinal location within a heat
exchanger. The crimp-spanning portion 430 is coupled to the insertion
portion 420 and configured to arch over and span the crimp 234 of FIG. 2.
The mounting portion 440 is coupled to the crimp-spanning portion 430 and
configured to allow the baffle 300 to be attached to another structure
(e.g., the faceplate of FIGS. 2 and 3). When the baffle 300 is attached
to the other structure, the body 410 becomes located at the predetermined
longitudinal location and is laterally constrained within the heat
exchanger.

[0045] The body 410 also has a longitudinal slot 450 having a
predetermined width and position. When the baffle 300 is attached to the
other structure, the slot 450 is also oriented relative to the heat
exchanger. In the illustrated embodiment, assuming the heat exchanger is
properly mounted in the furnace for which it was designed, the slot 450
is oriented such that it is located at or at least near the top of the
body 410. In this orientation, normal convection causes a flame traveling
through the body 410 to rise toward, and perhaps partially exit, the slot
450.

[0046] The mounting portion 440 includes a hole 460 configured to receive
a fastener (e.g., a screw or bolt) that may be employed to attach the
baffle 300. The embodiment of FIGS. 7A-7E may be constructed of a single
piece of metal, perhaps a perforated sheet or metal mesh. In one
embodiment, the metal sheet is grade 310 stainless steel. In one
embodiment, the metal mesh is Kanthal D®, commercially available from
Sandvik AB of Sandviken, Sweden.

[0047] As can be seen particularly in FIGS. 7D and 7E, the body 410 has a
generally circular cross-sectional configuration. A flame (not shown)
enters an end of the body 410 proximate the insertion portion 420 and
rises toward the slot 450 as it travels toward and eventually exits a
distal end of the body 410. Unlike the embodiments of FIGS. 4A-4F and
5A-5E and like the embodiment of FIGS. 6A-6F, the length L7 of the
insertion portion 420 is such that the flame is partially quenched before
entering the body 410. However, unlike the embodiment of FIGS. 6A-6F, the
proximal end of the body 410 lacks an acutely angled entry. This has also
been found to reduce NOx production, e.g., to below 20 ng/J.
However, elevated CO levels result from the partial quenching, as noted
above. To reduce the CO levels, e.g., to acceptable levels, the
embodiment of FIGS. 7A-7F provides a further structure that extends from
the body 410 at an end thereof that is distal from the locating structure
420. It should be noted that the embodiment of FIGS. 7A-7F is not
self-locating, therefore the further structure includes only a reactive
portion 640. The reactive portion 640 is exposed to air flow in the heat
exchanger such that its temperature elevates, configuring it to provide a
reactive surface adapted to create a reaction with respect to a
combustion product (e.g., CO). In a specific embodiment, the reactive
surface is adapted to cause CO to be converted into CO2, which as
stated above is generally regarded as being less harmful than CO. The
flame may at least partially exit the slot 450 depending upon the width
thereof.

[0048] FIGS. 7A-7E set forth various dimensions of the baffle 300. Table
4, below, gives example dimensions for a specific embodiment of the
baffle 300.